The www.alwaysinnovating.com TouchBook product line...
I've been following this company since it's inception about 3 years ago. Their tablets allow hot multi-OS switching between Android, Ubuntu, Chromium, and their proprietary Linux based OS. There are 4" and 9" models with optional detachable keyboards. The prices are relatively inexpensive and have some unique hardware and features.
I have yet to try any of them but would be interested to hear if anyone out there has used them and has an opinion about them.